JPS62123168A - Production of maleimide compound - Google Patents

Abstract

PURPOSE:To obtain the titled compound in high yield, by heating a maleinamidic acid in a specific inert organic solvent in the presence of an acid catalyst to effect cyclizing imidation of the acid and, after completion of the reaction, separating and recovering the acid catalyst from the organic solvent layer and recycling to the above reaction stage. CONSTITUTION:A maleimide compound is produced by the thermal cyclizing imidation of a maleinamidic acid of formula (R is 1-20C alkyl, phenyl, benzyl, etc.; preferably alkyl or phenyl) in a water-insoluble or water-immiscible inert organic solvent such as benzene, toluene or a petroleum fraction having a boiling point of 50-120 deg.C in the presence of an acid catalyst such as sulfuric acid, sulfuric anhydride, p-toluenesulfonic acid, etc. In the above process, the acid catalyst is separated and recovered from the organic solvent layer after completion of the reaction and the recovered catalyst layer is recycled to the above reaction stage and reused. The objective compound can be produced in high purity at a low cost with a simple process.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing maleimides. Specifically, when producing maleimides by ring-closing imidization of maleamide acids in the presence of an acid catalyst in a water-insoluble or water-immiscible inert organic solvent, the acid catalyst that has been subjected to the reaction at least once is This is a method for producing maleimides in high yield by reusing the layer formed by the oxidation process as a catalyst.

[Conventional technology and its drawbacks]

Methods for producing maleimides have been studied for a long time. Among them, the most common method is to dehydrate and cyclize maleamic acid using a dehydrating agent such as acetic anhydride to produce maleimide. is also disclosed. That is,
This is a method in which maleic anhydride and an amine compound are reacted, and the resulting maleamic acid is dehydrated and ring-closing imidized in the presence of acetic anhydride and sodium acetate. This method requires more than the equivalent amount of expensive acetic anhydride to maleamic acid in the imidization reaction, and also requires a large amount of water to separate and recover the maleimide produced from the liquid after the imidization reaction. However, it has the drawback that it requires a large amount of cost to treat the wastewater of large amounts of acetic acid.

For these reasons, this method is too expensive to industrially produce imide compounds.

In addition, as disclosed in JP-A No. 53-68770, dimethylformamide, dimethyl sulfoxide, etc. can be prepared by reacting maleic anhydride and an amine compound in an organic solvent without isolating the maleamic acid produced. There is also a method of carrying out an ascites ring closure reaction in the coexistence of an aprotic polar solvent and an acid catalyst. However, this method uses a large amount of expensive and toxic aprotic polar solvents such as dimethylformamide, which increases the production cost of maleimide. There are problems such as increased losses due to deterioration of the solvent in the product, and difficulty in removing these aprotic polar solvents from the product maleimide due to their high boiling points. Therefore, it cannot be said that it is an excellent method.

Furthermore, as disclosed in Japanese Patent Publication No. 51-40078 and Mei No. 1, solvents such as toluene, xylene, and chlorobenzene having a boiling point of 80° C. or higher, chlorosulfonic acid, p-toluenesulfonic acid, There is also a method of carrying out thermal dehydration ring closure together with an acid catalyst such as benzenesulfonic acid, orthophosphoric acid, pyrophosphoric acid, or phosphorous acid, and distilling the water produced at this time out of the thread by azeotroping with a solvent. This method is superior to the above two methods in that it not only does not require a large amount of expensive dehydrating agents such as acetic anhydride, but also that the maleimide produced is easy to separate and recover.

However, in this method, chlorsulfone Fa
, p-toluenesulfonic acid, benzenesulfonic acid, orthophosphoric acid, pyrophosphoric acid, phosphorous acid, etc. are used in relatively large quantities, and the yield of maleimides is low, making it difficult to use as an industrial production method. is not economically satisfactory.

In this way, the currently existing methods for producing maleimides are
It has many problems and is not satisfactory for industrial implementation.

[Purpose and means]

Therefore, an object of the present invention is to provide a method for producing highly pure maleimides in a safe and simple manner at low cost.

1) The purpose is to produce maleimides by heating maleamic acids in a water-insoluble or water-immiscible inert organic solvent in the presence of an acid catalyst to undergo ring-closing imidization. This is achieved by a method for producing maleimides, which comprises separating and recovering the acid catalyst from the organic solvent layer after the completion of the ring-closing imidization reaction, and recycling the acid catalyst layer to the ring-closing imidization reaction step for repeated use.

The present inventors have extensively researched the synthesis reactions of maleimides. As a result of intensive study on the economical method of using the acid catalyst used in the reaction, we found that the acid catalyst used in the reaction is separated from the reaction system as a catalyst layer after the completion of the ring-closing imidization reaction. It has been found that it can be used again as a catalyst in ring-closing imidization reactions. In general, we completed the present invention with the surprising finding that not only does the reaction yield not decrease at all, but that if the acid catalyst that was once used for the reaction is used again for the reaction, the reaction yield is significantly improved. This is what led to this.

Common sense would predict that repeated use of an acid catalyst in a reaction would reduce its activity and therefore the reaction yield (for example, West German Patent No. 1
934791), this fact is completely unexpected.

In other words, the present invention provides a process for producing maleimides by heating maleamic acids in a water-insoluble or water-immiscible inert organic solvent in the presence of an acid catalyst to cause ring-closing imidization. This method for producing maleimides is characterized by separating and recovering an acid catalyst layer from an organic solvent layer after the imidization reaction is completed, and repeatedly using this acid catalyst layer in reactions.

The most distinctive feature of the present invention is that by repeatedly using the acid catalyst used in the imidization reaction, the acid catalyst is not only used economically, but also the reaction yield is improved. Further, depending on the case, a metal compound or a stabilizer may be present in the ring-opening imidization reaction.

The maleamic acid used in the present invention is usually easily obtained by reacting maleic anhydride with a primary amine, and is represented by the following general formula (2).

(However, in the formula, R represents an alkyl group having 1 to 20 carbon atoms, a phenyl group, a benzyl group, a cyclohexyl group, a pyridyl group, a quinoline group, and those having halogen substitution, carboxyl group substitution, or nitroIH substitution on these groups) (preferably an alkyl group or a phenyl group.) In particular, primary amines suitable as raw materials for the maleamic acids used in the present invention include methylamine, ethylamine, n- Propylamine, isopropylamine, n-butylamine, sec-butylamine, isobutylamine, tert-butylamine, n-hexylamine, n-dodecylamine, arylamine, benzylamine, cyclohexylamine, aniline, nitroaniline, aminephenol, aminobenzoin acid, anisidine,
Examples include ethoxyphenylamine, monochloroaniline, dichloroaniline, toluidines, xylidines, and thylanilines.

The synthesis of maleamic acid is carried out almost chemically,
The amount of amines is equivalent to 1 mole of maleic anhydride.

However, in the case of industrial preparation, it is also possible by reacting 18 to 1.5 mol, preferably 0.9 to 1.2 mol, of IJO.

The organic solvent used in the present invention is preferably a water-insoluble or water-immiscible solvent that is inert to the reaction, such as bempine, toluene, petroleum distillate with a boiling point of 50 to 120°C, xylenes, ethylbenpine. , isopropylbenpine, cumene, mesitylene, tert-butylbenzene, pseudocumene, trimethylhekyrin, octane,
tetrac 1 col] Nikun, nonane, chlorobenzene, edilsik I cohe-1:su~n, petroleum distillate with a boiling point of 120-170°C, m-dichlorobenzene, 5ec-butylbenzene, p-dichlorobenpine, decane, p- Simen, 0
．． 9 No dichlorbenose, butylbenpine, decahydronaphthalene, 1-Rahyde naphthalene, dodecane, naphthalene, cyclohexylbenpine, boiling point 170-250
There are petroleum distillates etc. at ℃. The solvent used is 1 to 20 times the volume (volume ω) of 7-leinamide acid, preferably 3 to
Use 7 times ω times frequency. Further, b, which has a boiling point suitable for reaction condition A1, is selected while taking into consideration the solubility, price, handling, size, etc. of the maleimides. Furthermore, when considering the separation of the maleimide from the solvent after the completion of the reaction, it may be advantageous to use a low boiling point solvent and carry out the reaction under pressure.

As the acid catalyst, sulfuric acid, sulfuric anhydride, pt-toluenesulfonic acid, orthophosphoric acid, metaphosphoric acid, birophosphoric acid, etc. are used. The product used is 2 to 40% maleamic acid.
It is added in an amount of 0 mol %, preferably 20 to 200 mol %.

Further, depending on the case, a metal-containing compound and a stabilizer may be allowed to coexist in the reaction.

The acid catalyst added to the reaction system is used in the present invention.
Since it is difficult to dissolve in 11 solvents, the reaction system is essentially separated into two layers: an organic layer and a catalyst layer.

This state is the same during the reaction and after the completion of the reaction, but some reaction by-products and reaction intermediates are dissolved in the acid catalyst used for the ring-opening imidization reaction, and this is dissolved in the acid catalyst used for the ring-opening imidization reaction. When used in the reaction, it was found to have a very significant effect on improving the selectivity of the ring-closing imidization reaction.

Since this catalytic layer is a highly viscous liquid at room temperature, if it is used as it is for the next reaction, the temperature of the main catalyst layer to be handled should be 100 to 200°C, preferably 120°C.
~180°CPi! It is necessary to raise the level of liquidity and maintain liquidity. In addition, since the viscosity is significantly reduced by mixing water into the catalyst layer, it is preferable to add 5 to 20 weight percent of water to the catalyst layer in order to make it easier to handle at room temperature.

In addition, when separating the organic layer and the catalyst layer, when the temperature of the reaction solution becomes low, impurities dissolved in the organic layer will precipitate, and the interface between the two layers will not be sharp. Separation becomes difficult. Therefore, it is advantageous to separate 2P7i at high temperatures. Therefore, immediately after the completion of the reaction, 120 ~
It is preferable to separate the catalyst layer at a temperature of 250°C, preferably 130 to 220°C.

In some cases, the reaction may also be carried out in the presence of a metal-containing compound or a stabilizer. The metal-containing compounds used at this time include zinc, chromium, palladium, cobalt,
selected from oxides, acetates, maleates, succinates, nitrates, phosphates, chlorides and sulfates of at least one metal selected from the group consisting of nickel, iron and aluminum; Of these, zinc acetate is particularly effective. The amount of these used is 0.0 as metal per 1 mole of maleamic acid. OO5-0.5 mol%
Yes. Preferably it is 0.01 to 0.1 mol%.

Furthermore, as stabilizers, quinones such as methoxybenzoquinone, hydro-1; propionic acid esters, zinc dimethyldithiorubamate, dimethyldithiocarbamate Mu such as copper dimethyldithiocarbamate, salicylates, altetralylated diphenylamines, phenothiazine, phenothiazine such as medilene blue, 2-mercap-1 benzimidazole Mercaptoimidazole pheacyl phosphates such as are used.

The effect of these stabilizers is to allow the maleimide produced by the imidization reaction to exist stably under the high temperature of the imidization reaction without undergoing deterioration.

Regarding the addition of m, adding a small amount of m has little effect, and conversely, adding an excessive amount of m is not desirable because the amount of m added to the product becomes a problem. Therefore, the amount of these used is 0.00% per mole of maleamic acid. 0 0 5~0.5
It is mol%, preferably 0.05 to 0.3 mol%.

As a method of carrying out the present invention, first, an amine compound is added to a solution of maleic anhydride in an organic solvent, and the temperature is lower than 150°C.
Maleamic acid is obtained by reacting preferably at 30 to 120°C for 15 to 120 minutes. Next, without isolating the maleamic acid, the acid catalyst described above or the acid catalyst layer separated from the reaction system is added, and optionally a metal-containing compound and/or a stabilizer is added, and 120
~250°C, preferably 130~220°C for 1 hour~1
The reaction may be carried out while heating for 51 L'j and the water produced is distilled out of the system through azeotropic distillation, or the reaction may be carried out in a closed system without distilling it out of the system. Maleimides can be produced in high yield.

The present invention has been described above, and the advantages provided by the present invention are the following J-3.

(1) Maleimides can be produced in high yield by reusing as a catalyst an acid catalyst that has been subjected to at least one reaction.

(2) Since the acid catalyst is used repeatedly, the cost of the acid catalyst can be almost ignored.

(3) Since the acid catalyst is used repeatedly, there is virtually no need to detoxify the spent acid catalyst, and since it is a closed system, there is no need to worry about environmental problems due to acid disposal.

As described in (1) to (3) above, maleimides can be produced cheaply, safely and easily.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 Petroleum fraction 10 containing 98% or more of aromatic hydrocarbons with a boiling point in the range of 180 to 220°C was prepared in a flask equipped with a thermometer, a cooling tube equipped with a water separator, a dropping load, and a stirrer.
0g of anhydrous malein M 1 0 0 Q
was added to raise the temperature inside the flask to 100°C to dissolve maleic anhydride.

Next, 100 g of cyclohexylamine was added to 600 g of the above solvent.
A total of m of N-
A slurry of cyclohexylmaleamic acid in the above solvent was synthesized.

Next, add ortholin to the slurry liquid above? 160 g was added, heated and kept at 210° C. with stirring, and reacted for 2 hours while distilling water produced by the reaction out of the system together with the solvent.

After the reaction was completed, the lower acid catalyst layer was separated and removed from the reaction solution at 200°C.

Subsequently, the temperature of the reaction solution was lowered to 60°C, 100 g of water was added, and the mixture was stirred and washed with water for 30 minutes, and the aqueous layer was separated. After repeating this operation twice, 5 mm1-IQ (
abs) and the solvent was distilled off under reduced pressure.

Next, 0.3 g of silver dibutyldithiocarbamate was newly added to the flask, and 5 ml of l-I CJ (abs) was added.
N-cyclohexylmaleimide was distilled under reduced pressure over 30 minutes while maintaining the internal temperature at 130 to 150°C. As a result, 137 g of bright white crystals of N-cyclohexylmaleimide were obtained. The purity of this product was 99.8% by weight, and the yield was 75% based on the raw material cyclohexylamine.
．． This corresponds to 7 mol%.

Next, the same procedure was repeated except that an acid catalyst layer separated from the reaction system was used instead of orthophosphoric acid.
-Colorful white crystals of cyclohexylmaleimide 15
I got 39. The purity of this material is 99.81ω%,
The yield is 84.7 E based on the raw material cyclohexylamine.
Corresponds to Le%.

Example 2 Ortho-xylene 1 was placed in a flask equipped with a cooling tube equipped with a jQ 1α meter, a moisture N] container, a dropping funnel J3, and a stirrer.
00 g of maleic anhydride was added thereto, and 100 q of maleic anhydride M was added thereto, and the temperature in the flask was raised to 100° C. to dissolve the maleic anhydride.

Next, a solution of 100Q of cyclohexylamine dissolved in 60o9 of ortho-xylene was added dropwise in 1 hour under stirring to synthesize a slurry of ortho-xylene of N-cyclohexylmaleamic acid.

Next, 60g of Ortholin M and 0.1<J of silver dibutyldithiocarbamate were added to the above slurry liquid, heated and maintained at 143°C with stirring for 7 hours while distilling water produced by the reaction out of the system together with ortho-xylene. Made it react. After the reaction was completed, the lower acid catalyst layer was separated and removed from the reaction solution at 143°C.

Subsequently, the temperature of the reaction solution was lowered to 60° C., 100 g of water was added, and the mixture was stirred and washed with water for 30 minutes, and the aqueous layer was separated. After repeating this operation twice, 10InInHQ (ab
The ortho-xylene in step s) was distilled off under reduced pressure.

Next, 0.3 g of silver dibutyldithiocarbamate was newly added to the flask, and 5 tml l-1 (J (abs)
Distillation of 4-silmaleimide to N-Schiff[I was carried out over 30 minutes under reduced pressure of 130 to 150° C. while maintaining the internal temperature at 130 to 150°C. As a result, 146 g of bright white crystals of N-cyclohexylmaleimide were obtained. The purity of this product is 99.8
The yield is 80.6 mol% based on the raw material cyclohexylamine.

Next, the same procedure was repeated except that an acid catalyst layer separated from the reaction system was used instead of orthophosphoric acid.
-Colorful white crystals of cyclohexylmaleimide 16
I got 0g. The purity of this material is 99.8%,
The yield corresponds to 88.5 mol% based on the starting material cyclohexylamine.

Example 3 Ortho-xylene 100Q was charged into a flask equipped with a thermometer, a cooling tube equipped with a water separator, a dropping row 1~ and a stirrer, and anhydrous maleic Ml 00q was added thereto to set the eddy current in the flask to 100°. C to dissolve maleic anhydride.

Then, a solution of 100 g of cyclohexylamine dissolved in 600 g of ortho-xylene was added dropwise in 1 hour under stirring to synthesize a slurry of N-cyclohexylmaleamidic acid in ortho-xylene.

Next, 60 g of orthophosphoric acid and 0.1 g of silver dibutyl didiochlorbamate were added to the slurry liquid, heated and kept at 143° C. with stirring for 7 hours while distilling water produced by the reaction out of the system together with ortho-xylene. Made it react. After the reaction was completed, the lower acid catalyst layer was separated and removed from the reaction solution at 143°C.

Next, in the above reaction, the same operation was repeated except that a precursor layer separated from the reaction system was used instead of orthophosphoric acid, and the relationship between the number of reactions and the reaction yield was investigated. Table 1 shows the relationship between the number of reactions and the reaction yield. I got the results.

The reaction yield was measured by analyzing the liquid after the completion of the reaction by gas chromatography.

Table 1 Number of reactions Acid catalyst Yield (mol%
amine) 1 Orthophosphoric acid 84.3 Acid catalyst layer 5 Same as above 92
．． 810 Same as above
93.320 Same as above.
93.6 Example 4 A flask equipped with a thermometer, a cooling tube equipped with a water separator, a dropping funnel, and a stirrer was charged with a solution obtained by dissolving maleic anhydride powder 53a in xylene 50q. Next, the temperature inside the flask was adjusted to 130° C., and a solution prepared by dissolving 50 g of aniline in 400 g of xylene was added little by little over 30 minutes to synthesize a xylene slurry of N-futinylmaleamide acid.

The slurry thus obtained contained 10 g of orthophosphoric acid, 0.034 Q of zinc acetate, and 0.0 g of paramethoxyphenol.
After the reaction was completed, the acid catalyst layer was separated from the reaction system. After that, it was cooled to 30°C, washed with water for 11 hours, and the xylene was reduced to RF: 85g of N-notonilmaleimide crystals distilled off with
I got it. The purity of this crystal was determined by liquid chromatography to be 93.1 rfL suspension %, and the yield of this crystal was equivalent to 85.1 mol % based on aniline.

Next, the same operation was repeated except that an acid catalyst layer in which the reaction system had been separated was used instead of orthophosphoric acid, and 92 g of N-phenylmaleimide crystals were obtained. The purity of this product was 93.6% by weight, which corresponds to 92.67% by weight based on aniline.

Example 5 A solution prepared by dissolving maleic anhydride 539 in chlorobenzene 200Q was charged into a flask equipped with a thermometer, a cooling tube equipped with a water separator, a dropping row 1, and a stirrer. Next, methylamine gas was blown in little by little at a rate of 4.3×10 −3 mol/min at 30° C. for 2 hours or t to obtain a white slurry of N-methylmaleamic acid. Subsequently, to 5 g of Ortholin M22, 0.1 g of phenothiazine] and 0.02 g of zinc acetate were added, and the mixture was allowed to react at a temperature of 134° C. for 2 hours. After the reaction was completed, the acid catalyst layer was separated from the reaction system. The mixture was then cooled to 40 DEG C. and filtered, and then chlorobenzene was distilled off under reduced pressure to obtain pale yellow N-methylmaleimide 450 with a purity of 92.1% by weight. The yield of this product corresponds to 72.5 mol% based on the raw material methylamine.

Next, the same operation was repeated except that an acid catalyst layer separated from the reaction system was used instead of orthophosphoric acid, and crystals 53q of N-methylmaleimide were obtained. The purity of b was 93.4 rli 8%, which corresponded to 86.4 mol% based on the raw material methylamine.

Example 6 In Example 4, instead of using the acid catalyst separated from the reaction system as it was, 70% water was added to it and the reaction was carried out under the same conditions. 7
Enylmaleimide crystal 93Q was obtained. The purity of this product is 93.4% by weight, which is 93.4% by weight based on aniline.
．． This corresponds to 4 mol%.

Example 7 1J with thermometer, cooling tube, dropping funnel, J3 and stirrer! xylene 100g in glass o 1~crepe
was charged, maleic anhydride I'16100q was added thereto, and the temperature in the flask was adjusted to 100°C to dissolve the maleic anhydride.

Then cyclohexylamine 1 in xylene 400C]
A solution containing ooq was added dropwise to the N-
A slurry of cyclohexylmaleimide acid in the above solvent was synthesized.

Next, 80 g of orthophosphoric acid was added to the slurry liquid, and the water was heated in a closed-loop system to bring the internal temperature to 1.
The reaction mixture was kept at 52°C for 3 hours. The pressure in this time series was 1.2 atm at the initial stage of the reaction, but it rose to 6.7 atm after 3 hours.

After the reaction was completed, the reaction mixture was cooled to bring the internal temperature to 130° C. (15), then returned to normal pressure, and the reactant was taken out and left to stand, and the reaction solution was clearly separated into two layers: an organic layer and a catalyst layer.

The Vfg (M) of this right blhη is 622 g, and the N-cyclohexylmaleimide content (according to measurement by gas chromatography is 22.8 ffl f
i1%. This corresponds to 78.5 mol% based on the raw material cyclohexylamine.

Subsequently, the same procedure was repeated except that an acid catalyst layer separated from the reaction system was used instead of orthophosphoric acid, and 670Q was obtained as an organic layer. In this, N-cyclohexylmaleimide content (2) was 24.5% by weight. This corresponds to 90.8 mol% based on the raw material cyclohexylamine.

Claims (1)

[Claims] (1) In a method for producing maleimides by heating maleamide acids in a water-insoluble or water-immiscible inert organic solvent in the presence of an acid catalyst to cause ring-closing imidization, the ring-closing imidization reaction is completed. A method for producing maleimides, characterized in that an acid catalyst layer is subsequently separated and recovered from an organic solvent layer, and the acid catalyst layer is recycled to the ring-closing imidization reaction step for repeated use.